Portable electronic devices, such as those configured to be handheld or otherwise associated with a user, are employed in a wide variety of applications and environments. Increasingly, such devices are equipped with one or more sensors or other systems for determining the position or motion of the portable device. Notably, devices such as smartphones, tablets, smart watches or other portable devices may feature Global Navigation Satellite Systems (GNSS) receivers, low cost Micro Electro-Mechanical Systems (MEMS) inertial sensors, barometers and magnetometers. GNSS and multi-sensors can be integrated to provide promising positioning results in most outdoor environments. However, some mass market applications require seamless positioning capabilities in all kinds of environments such as malls, offices or underground parking lots. In the absence of GNSS signals in indoor environments, the conventional strapdown Inertial Navigation System (SINS) that uses low cost inertial sensors, suffers significant performance degradation due to the accumulated sensor drifts and bias. As such, positioning technologies relying solely on motion sensors may not satisfy all requirements for seamless indoor and outdoor navigation applications.
Pedestrian Dead Reckoning (PDR) is an example of portable device indoor/outdoor positioning techniques, and has become the focus of industrial and academic research recently. Similar to the SINS, PDR accumulates successive displacement from a known starting point to derive the position. This displacement (step length) can be estimated with various algorithms within a certain accuracy using the inertial sensor measurements. The position error using step lengths from PDR accumulates much slower than that from the accelerometer derived displacement from SINS. The PDR shows improved performance over SINS without GNSS updates. However, PDR still lacks robustness because of the accumulated heading error. This shortcoming may cause a skewed path over time and produce position estimates that might not be consistent with the building layout. Therefore, the resulting navigation trajectories may cross walls, floors or other obstacles. In order to avoid these types of navigation trajectory and building layout inconsistencies, map information may be used to constrain the PDR solution to areas indicated as possible routes or a determined position may be updated to match an assumed position derived from map information.
Accordingly, it would be desirable to provide navigation techniques using available map information to enhance the accuracy and reliability of positioning applications for portable devices. It would similarly be desirable to provide map information aided techniques that operate well with seamless outdoor and indoor transition as well as handling multi-level indoor maps to reliably navigate a user in a complex multi-level indoor environment. It would further be desirable to provide map information aided techniques that may be applied subsequently so as to benefit from post facto information and processing techniques. Moreover, it would be desirable to provide map aided techniques adapted for efficient operation in client and server modes, by enabling a server to use uploaded navigation solutions of a user to subsequently generate map matched results to enhance one or more of the solutions. As will be described in the following materials, this disclosure satisfies these and other needs.